Measurement range of E-Ex and E-Eφ wide field electromagnetic methods
Li Diquan1,2,3
1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, Central South University, Changsha, Hunan 410083, China; 2. Hunan Key Laboratory of Nonferrous Resources and Geological Hazard Detection, Changsha, Hunan 410083, China; 3. School of Geosciences and Info-Physics, Central South University, Changsha, Hunan 410083, China
Abstract：WFEM electromagnetic field intensity and apparent resistivity curves suffer serious distortions,when its measurement exceed the range of -30°~30° in the perpendicular direction and the range of -20°~20° in the axial direction of the dipole.So its measurement range should be redefined.Using half space model for numerical simulation,we analyze the variation of the antenna direction,EM field,and apparent resistivity with the angle,and discuss E-Ex and E-Eφ measurement range.Based on our research,the best measurement range for E-Ex WFEM covers 30° area of the both sides of the perpendicular direction and 20° area of both sides in the axial direction of the dipole; the best measurement range for E-Eφ WFEM is 60° area on the both sides in the perpendicular direction of the dipole.For E-Ex WFEM,the broadside line length is about 1.15 times of the vertical offset; and for E-Eφ WFEM,the line length is up to 3.46 times of the vertical offset.It is suggested to use E-Ex WFEM on 30° area of both sides in the perpendicular direction and 20° area of both sides in the axial direction of the dipole,and use E-Eφ WFEM on 30°~60° area of both sides in the perpendicular direction.
李帝铨. E-Ex和E-Eφ广域电磁法测量范围[J]. 石油地球物理勘探, 2017, 52(6): 1315-1323.
Li Diquan. Measurement range of E-Ex and E-Eφ wide field electromagnetic methods. Oil Geophysical Prospecting, 2017, 52(6): 1315-1323.
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